Malformations of the central nervous system are the second most common congenital anomalies, the highest being congenital heart disease.  With the advent of routine obstetric ultrasounds and anomaly scans the diagnosis are made in the antenatal period. Dandy-Walker syndrome is are complex developmental anomaly of the fourth ventricle .
There are a number of manifestations of the syndrome and they can be variable. The children usually present with slow motor development with delayed milestones. They may also show symptoms of increased intracranial pressure due to hydrocephalus, and these include irritability, vomiting and convulsions. They also present with macrocrania.
The other signs and symptoms are variable, depending on the extent of other malformations in the organ systems such as cardiac symptoms .
Central nervous system structures should be evaluated in all basic obstetric ultrasounds. If there are any noted malformations then neurosonography should be performed by medical professionals with expertise in this area.
Genetic testing is done for the known genes if a genetic component is suspect, due to higher recurrence rates in siblings. Beyond this there routine investigations are indicated and dependent on the other malformations noted.
Ultrasonography during pregnancy is the best available option, but if there is uncertainty then magnetic resonance imaging may provide additional information that may influence subsequent decisions concerning the pregnancy. For the children who have the suspected malformations, magnetic resonance imaging is the gold standard in making the diagnosis. CT scans are not advised due to the radiation. Other modalities such as echocardiography may be used to assess the associated cardiac anomalies .
Prognosis is dependent on the severity of the malformations that are present and the associated malformations such as cardiac defects. Individuals with more significant malformations having worse prognosis and outcomes.
The malformations in Dandy-Walker syndrome are due to defects in early embryonic development of the cerebellum and its surrounding structures. The characteristic triad includes complete or near complete agenesis of the cerebellar vermis, cystic dilatation of the fourth ventricle and an enlarged posterior fossa with displacement of the above tentorium and torcular herophili upwards. There are many possible causes of the Dandy-Walker syndrome, but it has been noted that chromosomal aneuploidy and various exposures such as rubella and alcohol during early pregnancy (this is thought to account for most of the cases) are common etiologic factors. There are also a fee gene deletions associated with the syndrome, such a chromosome 3q2 deletions, the location of the ZIC1 and ZIC4 genes  .
Dandy-Walker syndrome is rare with estimates ranging from 1 in 25,000 to 1 in 30,000 newborns. It is more predominant in female babies. Recurrence in siblings may be high when there is a genetic component like a single gene aberration, but the recurrence maybe associated with persistence of environmental factors. It accounts for approximately 1 to 4% of the cases of hydrocephalus .
The vermis completes its formation at about 13 to 14 postmenstrual weeks (or as late as the 16th week). Insults to the development of varying degree are believed to contribute to the genesis of the malformation. There have been a number of theories, but dysembryogenesis of the hindbrain is thought to be the insisting event that leads to the arrest in the formation the hindbrain, with lack in the fusion or the cerebellar hemispheres .
Timely obstetric ultrasounds and genetic testing for suspect inherited cause should be conducted to make decisions about the management of the pregnancy. Genetic counselling is needed for those families found to have the genetic aberrations. Avoidance of identified environmental causes such as alcohol is necessary. Vaccination against rubella to all females in their child bearing years is recommended .
The Dandy-Walker syndrome is a rare central nervous system congenital malformation that primarily affect the fourth ventricle (cystic dilatation) and cerebellar vermis, with enlargement of the posterior fossa. The Dandy-Walker syndrome may include malformations of the genital-urinary system, cardiac system and face and polydactyly .
Definition: Dandy-Walker syndrome is a condition that causes abnormal brain development, during the early parts of pregnancy. It primarily affects the part of the brain that coordinates movement, the cerebellum. There may be other malformations in the heart, face and digits.
Cause: It may be caused by genetic problems, but this account for a few cases. Most of the cases are thought to be caused by environmental toxins and some infections. These factors include alcohol ingestion during pregnancy. Infections such as rubella in the first trimester are thought to be a cause as well.
Symptoms: The major symptoms are due to increased pressure in the head due to fluid accumulation. This can be evident by a large head, irritability, vomiting, and slow mental development and coordination. Other symptoms such as a staggering gate may be noted. Hyperactivity may also be evident.
Diagnosis: The diagnosis can be made on a routine obstetric ultrasound but more specialized doctors should be the ones doing the scans if the malformation is suspected in previous scans. In young children magnetic resonance imaging of the brain is the best modality. Genetic tests may be also done to look for the genes that cause this syndrome, because if present there is an increased risk of following pregnancies having the malformations.
Treatment: Treatment includes reliving pressure in the brain by placing a tube in the brain and diverting the fluid. The rest of the treatment is supportive and includes occupational and physical therapy. The children may require special schools to assist with their learning difficulties. Genetic counselling may be required in families found to have a gene problem causing Dandy-Walker syndrome.